Neurophysiologie clinique = Clinical neurophysiology
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Review
Cognitive aspects of nociception and pain: bridging neurophysiology with cognitive psychology.
The event-related brain potentials (ERPs) elicited by nociceptive stimuli are largely influenced by vigilance, emotion, alertness, and attention. Studies that specifically investigated the effects of cognition on nociceptive ERPs support the idea that most of these ERP components can be regarded as the neurophysiological indexes of the processes underlying detection and orientation of attention toward the eliciting stimulus. ⋯ In such a theoretical framework, pain is seen as an epiphenomenon of warning processes, encoded in multimodal and multiframe representations of the body, well suited to guide defensive actions. The findings here reviewed highlight that the ERPs elicited by selective activation of nociceptors may reflect an attentional gain apt to bridge a coherent perception of salient sensory events with action selection processes.
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Several papers were published since the first clinical applications of laser evoked potentials (LEPs) in disorders of the nociceptive system. While studies produced until five years ago were mostly addressed at identifying lesions of the nociceptive system, more recent papers used LEPs as an instrumental tool for the diagnosis of neuropathic pain. ⋯ This is of utmost importance, as pain treatment should take physiopathological mechanisms, rather than etiology into account. Although there are still some limits for the routine use of LEPs as a diagnostic tool, this review of the literature demonstrates that LEP recording has become mandatory for the functional assessment of patients with hypoalgesia or neuropathic pain.
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Neurophysiological techniques help in diagnosis, prognosis and treatment of chronic pain, and are particularly useful to determine its neuropathic origin. According to current standards, the diagnosis of definite neuropathic pain (NP) needs objective confirmation of a lesion or disease of somatosensory systems, which can be provided by neurophysiological testing. Lesions causing NP mostly concern the pain-temperature pathways, and therefore neurophysiological procedures allowing the specific testing of these pathways (i.e., A-delta and C-fibres, spino-thalamo-cortical tracts) are essential for objective diagnosis. ⋯ Neurophysiological techniques not exploring specifically nociception, such as standard nerve conduction velocities (NCV) and SEPs to non-noxious stimulation, should be associated to the exploration of nociceptive systems, not only because both may be simultaneously affected to different degrees, but also because some specific painful symptoms, such as paroxysmal discharges, may depend on specific alteration of highly myelinated A-beta fibres. The choice of techniques is determined after anamnesis and clinical exam, and tries to answer a number of questions: (a) is the pain-related to injury of somatosensory pathways?; (b) to what extent are different subsystems affected?; (c) are mechanisms and lesion site in accordance with imaging data?; (d) are results of use for diagnostic or therapeutic follow-up? Neuropathic pain (NP) affects more than 15 million people in Western countries, and its belated diagnosis leads to insufficient or delayed therapy. The use of neurofunctional approaches to obtain a "physiological photograph" of somatosensory function is therefore highly relevant, as it yields significant clues about the type and mechanisms of pain, thus prompting rapid and optimised therapy.
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Comparative Study
Pain-related evoked potentials: a comparative study between electrical stimulation using a concentric planar electrode and laser stimulation using a CO2 laser.
To compare the pain-related evoked potentials (PREPs) obtained by superficial electrical stimulation using a concentric planar electrode to those obtained by CO2 laser stimulation. ⋯ The estimated CVs of the recruited nerve fibres and the localized pinprick sensation felt by the subjects suggest that small-diameter fibres in the A-delta range, conveying "first-pain" information, were stimulated in response to superficial electrical stimulation as for laser stimulation. Superficial electrical stimulation using a concentric planar electrode could be a valuable alternative to laser stimulation for assessing PREPs in the practice of clinical neurophysiology.
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Our scientific activity is focused on the field of action and representation of action from various adaptative situations during the life span, including pathology and extreme environment such as microgravity. The early action/perception matching, subserving the motor simulation network, is probably a major milestone for the building of action and representation of action during the course of ontogenesis. We have developed a functional approach of motor development based on a gradual mastering of coordination, adaptation and anticipation in postural control in the course of ontogenesis from babies to adolescents. ⋯ The second step consists in learning to select postural strategy depending on the characteristics of the task and the environmental requirements. An appropriate selection means to anticipate the consequence of the movement in order to maintain balance control and efficiency of the task. Taking into account the complexity of the parameters to control and the late maturation of anticipation and representation of action, it is not surprising that the development of postural control continues up to late periods during childhood and adolescence.